Your Bones

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A question sent to Author Lara Pizzorno from a reader of Your Bones:

TO: Lara Pizzorno

I read "Your Bones," and first, want to thank you for it. I'm sure it will help many people. I'd like your thoughts on something that I have been trying to get an answer to for years. I read that strontium can slant a bone density test by making it appear like there is more bone than there actually is. I also read that, for this reason, strontium should be stopped 2 weeks prior to the test. Is this true? If so, perhaps it's something you can add to your book if you print another edition someday.

I'd appreciate your thoughts on this and thanks again so much for your book and your discussion on Coast to Coast.

Patty

Lara's Answer

Hi Patty,

To try to provide you with a more definitive answer to your concerns that strontium causes a grossly inflated (and inaccurate) DEXA BMD result, I ran another PubMed search using “dual-energy X-ray absorptiometry”— i.e. the full spelling of DEXA (which they also refer to as DXA), and found several much more recent studies than the ones cited on the “www.osteopenia3.com” website.

Yes, it appears to be true that strontium affects DEXA results. Strontium has a larger atomic number (Z=38) than calcium (Z=20). This causes the DEXA BMD reading to be overestimated by ~10%. And because this is due to the atomic weight of strontium vs. calcium, this will be the case regardless of the form of strontium used—strontium ranelate or citrate.

However, the real question is what is the impact of strontium on the health of your bones? What does this mean in terms of your risk of fracture if you are taking strontium? Does strontium effectively reduce your fracture risk or not? Happily, the studies clearly show that it does.

Bottom line:

(1) As Dr. Wright and I recommend in Your Bones, take more calcium than strontium (I get more than twice—probably 3 times as much calcium as I do strontium when I add up not only the calcium in my supplements, but the calcium in my typical diet. Thus, strontium is assisting, but calcium remains the predominant mineral in my bone matrix.)

(2) Take calcium at a different time of day from strontium (I take mine at lunch, but the drug company that sells strontium ranelate says to take it 2 hours away from all food to maximize absorption—my bones are steadily rebuilding, so I feel no need to be this stringent; however, for someone with full-blown osteoporosis, the extra hassle is likely to be worth putting up with to quickly lessen fracture risk. Directions given by the manufacturer of strontium ranelate are to take it at night on an empty stomach before bed. You could take calcium [in the form of calcium citrate or hydroxyapatite] first thing in the morning and at lunch then take strontium citrate at night.)

(3) If you are taking strontium, be aware that your DXA results may be 10% inflated; however, also be aware that strontium is increasing your BMD, greatly decreasing your risk of fracture, and both stimulates bone-building osteoblasts while also toning down excessive old-bone-removing osteoclast activity.

If you would like more insight into my basis in the research for the above bottom line conclusions, I’ve copied in some of the key text from the most recent articles for you below.

Here’s a quote from a much more current paper (published in 2007) on this issue than the one cited on “www.osteopenia3.com” (the study cited there was published in the journal Bone in 1997):

“… the results of the SOTI and TROPOS trials confirm that strontium ranelate is a safe and effective treatment for preventing vertebral and hip fractures in postmenopausal women with osteoporosis. The 40% reduction in vertebral fracture risk after 3 yr treatment is similar to that for several other osteoporosis therapies. Strontium ranelate has also been shown to reduce nonvertebral fracture risk by 15% and to reduce hip fracture risk in older women with osteoporosis. Strontium ranelate is the only osteoporosis treatment proven to be effective at preventing both vertebral and nonvertebral fractures in patients aged 80 yr and older… Data from animal studies and bone biopsies suggest that there is an improvement in bone quality and bone strength. Although the large BMD increase that occurs during strontium ranelate treatment provides a useful tool for patient monitoring, clinicians should be aware that much of this increase is due to increased X-ray attenuation because of the incorporation of strontium into bone.” (Pub Med Reference: Blake GM, Lewiecki EM, Kendler DL, et al. A review of strontium ranelate and its effect on DXA scans. J Clin Densitom. 2007 Apr-Jun;10(2):113-9. PMID: 17485027)

Here are further quotes from the most recently published (2009) PubMed paper on this (PubMed Reference: Barenholdt O, Kolthoff N, Nielsen SP. Effect of long-term treatment with strontium ranelate on bone strontium content. Bone. 2009 Aug;45(2):200-6. Epub 2009 Apr 17. PMID: 19376283) :

“…strontium ranelate–treated patients show large increases in BMD coupled with comparatively modest changes in biochemical markers and bone histology. Much of the BMD increase is due to the higher atomic number of strontium (Z = 38) compared with calcium (Z = 20). DXA scanners measure BMD through the increased attenuation of X-rays by the photoelectric effect, which varies as the third power of the atomic number (Z3). If 1% of calcium atoms in hydroxyapatite are replaced by strontium, BMD measurements are increased by 10% although the net mass of bone mineral increases by only 0.5% (8) and (9). Therefore, if sufficient strontium is present in bone it can cause a clinically significant overestimation of BMD compared with the true mass of bone mineral that would be found by the conventional gold standard of bone densitometry, a bone ashing study.” (NOTE that strontium does cause a net increase in BMD of 0.5%)

“…each 2 gram dose of strontium ranelate delivers 680 mg of elemental strontium” (FYI -- Strontium ranelate is given in a packet containing 2 grams of little granules that deliver 680 mg of elemental strontium in one daily dose.)

“As the absorption of strontium ranelate is competitive with calcium, calcium supplements should be taken at a different time of day to avoid reducing strontium absorption. Similarly, absorption is affected by food, milk, and milk derivatives, so that strontium ranelate should be taken at least 2 hours after these products.”

The 2 most important requirements of any osteoporosis treatment are its antifracture efficacy and safety. For strontium ranelate, these data come from the SOTI and TROPOS studies. In the SOTI trial, at the end of the first year, women taking strontium had a 49% lower risk of a new radiographic [seen on x-ray] vertebral fracture compared to women given a placebo. The risk of a clinically symptomatic vertebral fracture was 52% lower. After 3 yr, the strontium group had a 41% lower risk of a new radiographic fracture & the incidence of clinically symptomatic vertebral fractures was 38% lower. Recently the 4-yr data were reported and show a 33% reduction in radiographic vertebral fractures. In the TROPOS study, over 3 yr, the reduction in vertebral fracture risk was 39% and was similar even for patients who had already had a vertebral fracture when the study began. The recently reported 5-yr data showed a 24% reduction in vertebral fracture risk.

A key aspect of the SOTI and TROPOS studies was the advanced age of many of the subjects compared with many previous osteoporosis trials. 23% of the combined study populations were aged 80 yr or older at enrollment. In women older than 80 yr, strontium ranelate demonstrated a 55% reduction for vertebral fractures over the first year of treatment and 32% over 3 yrs.

Here’s one last quote, this one from the “Comment” (Comment = a discussion of the 2009 paper), which was also published in the same journal (Reference: Belissa-Chatelain P, Dupin-Roger I, Cournarie F, et al. Re: "Effect of long-term treatment with strontium ranelate on bone strontium content" by Barenholdt et al. (Bone, 2009). Bone. 2009 Nov;45(5):1024-5; author reply 1026-7. Epub 2009 Jul 17. PMID: 19616656):

“Strontium ranelate treatment increases bone mass and reduces the vertebral, non vertebral and hip fracture risk. The measured non adjusted BMD allows to evaluate at the individual level the response to the treatment, is predictive of the fracture risk reduction, and leads to discernable increases in BMD, useful to overcome the precision error of the DXA instruments.”

So, what they are saying is yes, BMD as measured by DXA will be over-estimated in people taking strontium, but nevertheless, strontium treatment increases bone mass and reduces fracture risk. DXA is useful in that it shows whether the patient is responding (absorbing strontium well), and a better DXA score still correlates with lower risk for fractures.

I hope this alleviates your concerns. I very much appreciate your bringing this issue to my attention; I’m sure others will also hear about this and will be wondering what’s up. Praktikos will be posting “research updates” related to Your Bones on their website, so we can make this information, and anything else I see in the breaking research relevant to bone health, available to others.

Do keep me posted on how you are doing. I wish you every happiness, including great bones!

Lara